Venus Williams believes sister Serena stands a "pretty good chance" of completing the calendar Grand Slam - even though she could be the player who ends the dream.
While Serena battled through a tough opener on Monday at Wimbledon, Venus swept to her first 'double bagel' at the championships, a 6-0 6-0 win against fellow American Madison Brengle.
The sisters have gone head to head in four Wimbledon finals and this year are seeded to meet in the fourth round next Monday, potentially an occasion to truly savour.
"It would be great if I can continue to play well and get there, play next week. That would be great," said Venus, who at 35 is the elder sister by 15 months.
There is no point in Venus offering advice, she says. Serena, after all, is pursuing a 21st grand slam title this fortnight, and to hold all four at the same time for the second time in her career, having won the US Open last September and begun this year with the Australian Open and French Open titles.
"I don't think she necessarily needs any advice from me or probably anyone. She should be giving out the advice," said Venus.
"I think we just all try to keep her encouraged. I think we're all amazed at what she's done really."
The last player to win all four slams in the same calendar year was Steffi Graf in 1988. Serena may have been short of her best in beating 20-year-old Russian Margarita Gasparyan, but she still won emphatically, 6-4 6-1, and the historic target is in her sights.
"Obviously I think it's a pretty good chance," said Venus. "It hasn't been done that often. But then again, she's done a lot of things that haven't been done that often."
Serena has little enthusiasm for talking about the clean sweep but the 33-year-old acknowledges her game has hit remarkable heights since losing in the third round at Wimbledon a year ago.
"I've had such an amazing year, I ended up winning the (US) Open, the (WTA) Championships, the Australian and France. I couldn't have dreamt of a better 12 months. So it's been really great. I'm just excited about that and really focusing on that," Serena said.
"I always focus on the moment. I don't live too far in the future, and I don't live in the past, I just live in the present."
Former semi-finalist Victoria Azarenka coasted through her opening match. The 25-year-old Belarusian reached the last-four stage in 2011 and 2012, and overwhelmed Estonian Anett Kontaveit 6-2 6-1 in just 57 minutes on Court 12.
Serbian seventh seed Ana Ivanovic was watched by her footballer boyfriend Bastian Schweinsteiger as she enjoyed a swift 6-1 6-1 victory over China's Xu Yi-fan.
Few if any were as impressive as Venus Williams who torched the hopes of an opponent 10 years her junior late in the afternoon.
It took the five-time champion just 41 minutes on Court Three, firing six aces and 29 winners in all against an outclassed opponent.
There was remarkably another 6-0 6-0 victory minutes later as Andrea Petkovic of Germany inflicted the same humiliation on American Shelby Rogers, a 22-year-old who was making her Wimbledon debut.
Russian Maria Sharapova, the 2004, champion eased to a 6-2 6-2 win over Great Britain's Johanna Konta on Centre Court, and last week's Eastbourne champion, Switzerland's Belinda Bencic, recovered from a slow start to overcome Bulgarian Tsvetana Pironkova 3-6 6-1 6-3.